Answer:
1. O2
The oxygen molecule is a non-polar covalent molecule. It is formed by sharing of electrons. As the molecule is symmetric, the electrons are pulled by both the atoms in an equal amount.
2. CaO:
The association of two ions forms calcium oxide. The ions are calcium ion and oxide ion. Such a compound is called an ionic compound.
3. Br2:
Bromine molecule contains a non-polar covalent bond because both the atoms share an equal number of electrons, and it is symmetric.
4. HBr:
Hydrogen bromide is a polar covalent compound. It is an asymmetric charge between hydrogen and bromine. Bromine being more electronegative, tends to pull the electron itself.